This invention relates to the monitoring of radio frequency generator outputs and particularly to a circuit for monitoring such outputs.
Many types of radio frequency (RF) generating equipment are used in industry and elsewhere for the purpose of induced heating. These generators are subject to federal regulations and are periodically checked for compliance. Generator malfunctions including change of operating frequency, loss of output power and/or carrier modulation may occur in between checks or maintenance inspections. These malfunctions are likely to result in an improperly processed product or in other problems depending on the generator's application or use. A malfunction in the generator may not be apparent to an operator or to an automatic control system so that the problem may exist for a long time and result in a large amount of poorly manufactured goods.
A need exists for a method and apparatus to monitor the output of such RF generators to detect frequency drift, lack of output, and modulation of the RF carrier due to power supply ripple. Such apparatus should be light-weight, small and suitable for fixed installation or portable use. It also should provide indicator lights to signal when and if a fault exists and should provide for connection with automatic control equipment when used in a fixed installation. This apparatus could be used to perform a continuous or periodic check of RF generators, RF induction heaters, diathermy equipment (medical and therapeutic equipment) and other similar equipment. A particular application would be to monitor the output of an RF generator used for getter flashing of color picture tubes.